In petroleum and chemical industries, requirement is very high for fireproof, explosion-proof for manufacturing and storage facilities. Presently grounding connections are provided by bare screw connections. If such bare screw connections are exposed to rain, rust may cause disconnection. When the electrical current fluctuates due to thunder, arcing or shortage may also occur, causing fire or explosion accidents. On the other hand, if rusting causes a lightning rod to be disconnected, disasters could happen were the facility protected by the lightning rod struck by a lightning. In other instances, rusted screws may impede regular maintenance testing of the electrical connection, causing significant inconvenience.